DE2655460A1 - METHOD OF MANUFACTURING A PERMEABLED MICROPOROUS CERAMIC ELEMENT - Google Patents

Description

F- AT t £ N "A l · ! \ Νλ \ L '

A. GRUNECKER

DlPU-ING

H. KINKELOEY

DR-ING

W. STOCKMAIR

K. SCHUMANN

DR HER NAT. - DIPU-F = HYS

P. H. JAKOB

OIPU-IN &

G. BEZOLD

DfI HER NAT- CKPL-CHEM

8 MUNICH

MAXIMILIANSTRASSE

P II090 -60 / E: December 7, 1976

COMMISSARIAT AL ¹ ENERGY ATOMIQUE
29, rue de la Federation
75015 PARIS, France

Method of making a permeable microporous

Ceramic element s

The invention relates to a new method of sealing the ends of porous ceramic elements and the fixing of metallic end pieces (clamps) at these ends.

A blocking element (barrier) for the separation of gaseous Elements of a mixture generally consists of a mechanically resistant porous cylindrical support, whose Inner wall is coated by a thin layer of a pressed microporous powder, which separates the gaseous isotopes guaranteed.

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TELEKON (G8f>) 20 0862

TELEX 06-2S380

TELECOPICEP

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After the ceramic-type locking element has been manufactured, the ends must be fitted with two end pieces or ferrules (embouts) be provided that its assembly between two diffuser plates or its connection with other locking elements allow·

The material that ensures this fixation and the method of application of the same are of particular importance, as they affect the locking element, which is subject to considerable compressive loads, Can be exposed to tensile stresses, torsions and vibrations during its function, a must impart good mechanical resistance.

This fixation must in particular not have a fragility (brittleness) of the ceramic carrier, for example a Cracking, even if it is very partial, at the joints between the grains that make up the porous material build up, bring with it. It must also not lead to any dislocation or weakening of the permeable layer.

This fixation must also be a perfect seal of the Ensure the end of the locking element, so that the entire gas flow to be separated necessarily crosses the permeable layer, of course without bypassing it to escape through the carrier or through the thickness of the same.

This condition requires in particular that the adhesion of the sealing material and fixing material inside the Barrier element, i.e. on the microporous permeable layer, is just as good as on the front side (the cross-section) or on the outside of the support, which is very rough (uneven).

The adhesion must also be perfect with respect to the metallic end piece. For the sake of effectiveness of the separation of the

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Isotopes must match the length of the material which ensures the sealing of the locking element and the fixation of the end pieces, inside (on the side of the permeable layer) and outside (on the side of the carrier) of the blocking element be approximately the same.

It can therefore be said that this method of operation serves a double purpose: on the one hand, it is intended to achieve a perfect seal of the end of the locking element are guaranteed, and on the other hand, a mechanically very strong connection should be ensured of the metallic end piece (embout) can be achieved with this end.

Numerous materials and methods have been used to achieve the goals defined above.

Attempts have already been made to use certain metals or metal alloys which have been modified by additives which ensure the "wetting" of the ceramic parts can. This on the end of the locking element and However, the metal bodies melted (sintered on) of the end piece generally lead to a dislocation of the permeable ones Layer and to a considerable embrittlement (embrittlement) of the ceramic carrier, the can break spontaneously due to shrinkage. These alloys are often of complex composition to fluorine-containing agents to which they are exposed, hardly constant.

It has also been suggested to perform this operation by applying a coating of a fluorine-containing resin, such as trifluorochloroethylene, which is melted in the heat and has been polymerized, the locking element and the end piece having an outer shape with a inner punches (graver) are provided, these being open

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can and easily removed after the thermal treatment can be. However, the application of a resin does not lead to good adhesion to the end piece and this The disadvantage is that the whole thing has a relatively low mechanical strength. Adhesion to the microporous Layer is also often defective and there can often be leaks between the resin coating and it Layer can be determined. On the other hand, the viscosity of these coatings decreases as a function of temperature and in the course of the use of the locking element in the heat and with considerable mechanical stresses the coating a certain creep flow and the mechanical properties and the sealing increase considerably away·

As the process of sealing the end of the locking element and the simultaneous fixation of the end piece has proven difficult to carry out, it has been suggested to separate these two work steps from each other

The sealing of the ends of the locking element is carried out in such a way that they are placed in a suspensimvon dips powdered glass in a suitable liquid, dries it and heats it at a temperature which ensures the melting (sintering) of the glass layer. This enameling of the ends is carried out with a glass chosen for its good behavior in a corrosive atmosphere containing fluorine, for example with a glass based on phosphates and aluminum oxide

The glass layer applied to the outside of the support is then subjected to a sandblasting treatment * in order to give it a certain roughness. This roughened surface is then coated with a metal layer, for example with a copper layer, which is covered by *> with corundum grains ^ ^ _η

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'' Spraying in the heat using a flame torch (welding torch) is applied.

The metallic end piece is then placed on the end of the locking element coated on this V / eise and welded on (soldered) using a weld of a fusible (sinterable) alloy, for example with a tin-lead-silver alloy or a tin-lead-cadmium alloy, which both the end piece .als also "wets" the metal layer applied to the enamel on the ends of the blocking element.

This method involves a large number of operations that make it quite expensive (cumbersome) and it has major disadvantages that make it unusable for relatively high temperatures at which locking elements work do. The glass is against severe corrosion conditions of fluorinated (fluorine-containing) gases only very much incompletely resistant as well as the metal applied to the glass and the weld alloy that the Fixation of the end piece guaranteed. The mechanical properties of such an arrangement are relative after a short duration of function worse (impaired).

Another method used is that in a first stage a sealing of the locking element is carried out Applying a layer of a refractory mineral material such as aluminum oxide or solid solutions thereof or from compounds thereof with other oxides produced by hot spraying using a burner is applied with a chemical flame or a plasma torch.

The spray angle (spray angle) is chosen so that the inner section of the locking element (on the side of the

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permeable layer), the front side (the cross section) and the outer section (on the side of the carrier) be coated with a layer of this material.

In a second stage, after sealing, the end piece is joined to the end of the locking element and the whole thing is connected with a metal coating, which is also in the arm of the TV on the previously sandblasted end piece and on the dan Has been sprayed onto the end of the locking element.

This step has a number of disadvantages severely limit interest in it.

During the application of the oxide coating, which is intended for sealing the locking element, must be inside the same a rubber stopper can be placed which determines the coating length limited because the rebounding of the molten (sintered) refractory particles into one long layer with an irregular and discontinuous thickness which results in the effectiveness of the separation of the locking element interferes with (impaired). The presence of this stopper, which limits the length of the inner cover, leads to the formation of a bead or a thickening, which leads to a greater loss of charge of the longitudinal flow in the Locking element leads.

The adhesion of this oxide coating on the permeable layer (diffuse layer), especially if it is a very has a fine structure (small pore grooves) is very mediocre and there is often an escape between the permeable ones Layer and the oxide coating.

The oxide coating on the front side (the cross section) of the blocking element is very sensitive to mechanical pushing, and precautions must be taken home

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Positioning of the metallic end piece on mechanical \ 7ege to the locking element to prevent peeling (peeling) or breakage of the coating

Finally, the metal layer, which is intended to ensure the fixation of the end piece on the locking element, is not always absolutely tight and if the end piece is not perfectly attached to the end of the locking element leakage through the fixing metal may occur therebetween.

It should also be pointed out that all of the known methods described above relate to finished locking elements, i. on ceramic substrates to which the microporous separating layer has been applied.

If the seal fixation is inadequate, it must finally the completely finished locking element can be eliminated (eliminated) and this waste (scrap) is particularly costly.

The inventive method consists in that one Performs operation that ensures the sealing of the ends of the ceramic carrier, then the thin microporous separating layer is applied, which is then compressed (pressed together), heat-treated and optionally is adjusted in terms of their thickness, after which the metallic end pieces or ferrules (embouts) fixed on this finished blocking element (barrier).

This process is economical and technically easy to carry out and the number of operations is very limited. It ensures absolute sealing of the gas flow towards the interior of this locking element and a maximum Separation efficiency

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Its properties of resistance to mechanical Stresses are exceptionally good and its behavior in a corrosive atmosphere, especially in one containing fluorine Atmosphere is particularly good, and the locking element equipped in this way can be used when it is used are exposed to high temperatures and high aerodynamic loads without deterioration over time (Deterioration) can be determined.

After all, this type of sealing fixation does not entail any additional loss of charge for the longitudinal current, which circulates in the locking element.

The aim of the invention is a method for the production of porous elements made of oxide ceramic materials, characterized in that one ends of the porous tube, which forms the support of this element, is metallized by spraying a coating on in the heat the inner wall of the support in the form of a thin layer of a microporous powder, which is intended to make the separation of gaseous elements to ensure the applied layer is compressed (densified) and metallic end pieces (Forcing) fixed at the ends of this element by spraying a metal in the heat onto the end piece-element connection points

The porous tube, which is the support of the separating element, is subjected to a first treatment, which is therein consists in applying a metal layer to its ends by spraying it on in the heat using a suitable burner. This layer covers the outer wall that Front side (the cross section) and the inner wall of the beam over a limited length "

The inner wall of the support treated in this way is then coated with a thin layer in a manner known per se

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covered from a microporous material. The layer applied in this way is compressed by isostatic compression (pressed together).

The element produced in this way undergoes a thermal treatment and, if necessary, an adjustment subjected to its permeability, after which a cylindrical end piece with the end of the element so treated connected and attached to this element by means of a metal eyelet is fixed, which is sprayed onto the junction between the element and the end piece with a suitable burner will.

The invention is explained below with reference to preferred examples of embodiments of the invention with reference to the enclosed Drawings explained in more detail, but without being limited thereto. Show:

Fig. Λ a way of applying a metal layer to the end of the ceramic carrier,

Figure 2 is an enlarged view of the end of the carrier with its metal sealing layer and that applied thereafter microporous layer and

3 shows the end of the finished separating element with the separating element fixed thereon metallic end piece (ferrule)

In Fig. 1, the carrier 1, generally in the form of a cylindrical tube with a high porosity, considerable permeability, and consists of grains one or more metal oxides densified by sintering at elevated temperature and it is on a suitable mechanical device subjected to a rotational movement.

A metal layer 3 is applied to the end of the carrier with a spray device 2. At the fuel system

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it is generally a spray gun, which is the melting of a metal thread with a propane or Butane / oxygen or acetylene / oxygen flame guaranteed, The device for spraying the metal can also be a gun, which maintains an electric Arc between two threads of the metal that is to be applied, allows the metal to be coated Element with a gas jet or ηit oinea Plasma jet, which is fed by powder from the metal to be sprayed on, is sprayed on.

The choice of metal to be applied depends on a particular one Importance because it must be completely resistant to the chemical action of fluorine-containing corrosive gases, to which the element is exposed during its use. In addition, the metal in the applied form must have a retain certain ductility, which is its compaction in the subsequent operations and the achievement of a practical Dense coating between the microporous layer and the support allowed. Such a metal can be Trade winding or one of its alloys, with aluminum being particularly suitable and offering the necessary advantages.

The spray distance between the spray device (burner or pistol) and the carrier is chosen so that the metal particles impinge on the carrier in liquid form, without to heat it excessively. To avoid an increase in temperature, a compressed air blower can be applied to the end of the support Ground in the opposite direction to that of the spray device (torch or gun).

The spray angle is determined so that the length of the coating is limited to the desired length inside the tube. However, a certain number of particles bounce off the

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inner wall of the pipe back and leads to worse and partially interrupted (discontinuous) coating, depending on the effectiveness of the enrichment of the barrier element damage and lead to local defects. To avoid the deposition of these impacting particles, it is possible to direct a gas flow, in particular compressed air, to the opposite end of the blocking element, whose flow velocity is calculated in such a way that these impacting particles are repelled (repelled) without, however, the jet of directly from the Spritζ device escaping particles is cooled "

In order to limit the length of the metal coating, it is useful to extend the Spritζeinrichtung the pipe support as far as possible to approach, since, however, the rebounding of particles and above all an excessive heating of the pipe is avoided must be, however, the flow rates of the combustible gas and the oxygen carrier, the flow rate of the air and the introduction rate of the metal thread in the spray device to low values set The metal grains and especially the aluminum grains, those that are sprayed on with these special settings are also larger and less oxidized than those obtained with the usual settings made by the manufacturers of the flame scoring device are recommended, and they are more favorable for subsequent compaction of the coating. These settings can be used for the Implementation of the fixing of the end pieces described below are retained.

To limit the length of the coating on the outer wall of the pipe support, a protective plate (a Screen) 4 · between the pipe support and the spray device to intercept some of the sprayed-on parts.

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This protective plate is a metal plate or a plate made of a synthetic resin or a one that consists of a strip of paper running past, or around a plate made of glassy carbon according to a preferred embodiment of the invention.

After this treatment, both ends of the carrier are covered with a continuous metal layer covers, which envelops the outer wall, the end face (the cross section) and the inner wall, the Length of this layer on the outer wall and on the inner wall is about the same. It should be noted that these metal layers mechanically reinforce the ends of the beam, which is then subjected to subsequent manufacturing treatments of the separating element, whereby its sensitivity to impacts or other stresses is reduced very much.

The treatment described below consists of applying a thin layer of '' a microporous powder, which separates the gaseous compounds from each other guaranteed. This powder is obtained by filtering a suspension of said powder in a suitable solvent applied by the carrier.

It should be noted that the applied metal layer in the previous treatment has a thickness of the end decreases towards the interior of the carrier and the one zone of gradual transition from the dense metallic portion results in the porous ceramic portion, the permeable layer extending on the porous metallic Section can deposit, whereby a layer defect at the metal-ceramic boundary is avoided.

After the separation layer has been deposited and after the thermal elimination of the organic binders, which

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the suspension used for the application becomes the whole of an isostatic compression (Compression), which serves to compact (compress) the layer on the carrier and the To give the carrier the necessary structural properties (pore grooves, porosity, permeability).

Fig. 2 shows the end of the element thus obtained, where the number 1 denotes the porous ceramic support, the number 3 denotes the metal coating applied by spraying and the Number 5 denotes the separating layer, which is applied in a short length to the metal layer

After this compression (compaction), the whole is subjected to any thermal treatment that is necessary for this serves to desorb certain foreign bodies from the layer or the structure and properties of this layer thermal evolution of its elementary crystallites allow. This can also cause stress relief annealing the applied metal can be ensured, whereby all mechanical stresses to which the carrier can be subject, be eliminated. This process of adjusting the permeability can also be carried out before the heat treatment will.

As indicated in FIG. 3, the porous barrier element is made up of the carrier 1 and its metal coating at the end 3 and its inner separating layer 5 is provided with a metallic end piece (ferrule) 6, the outer diameter of which is slightly larger than the outer diameter of the element. This cylindrical end piece is in the axis of the element arranged and connected to the latter. This metallic end piece is attached by means of a metal layer 7, which is applied by spraying with a spray device on the two ends to be connected.

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Regarding the carrier, it is important that the length of the applied Metal does not exceed that of the layer during the first metallization of the carrier. To this end the position of the spray device is adjusted in relation to the distance and the firing angle and one can also. Use masks that limit this length.

As-with the metallization of the ends of the beam, the metal must be chosen so that there are severe chemical corrosion conditions completely resists when using the element. This metal can be nickel or a Acting nickel alloy, according to a preferred embodiment of the invention, however, aluminum is used because it the requirements for chemical behavior and the mechanical requirements as stated above are completely sufficient.

The end piece (ferrule) is also made of a metal that is completely resistant to fluorine-containing gases and can for example consist of a copper alloy. In this case, the surface of this end piece must be sprayed on by one Fixing metal is covered beforehand with corundum grains or shot are treated (sandblasted) to give it a certain roughness, which makes mechanical adhesion of the sprayed-on metal is allowed.

According to a preferred embodiment of the invention handolt the sprayed-on metal is aluminum or one of its alloys and the end piece is made of nickel or one of its alloys its alloys and in this case the latter is not sandblasted, but simply rubbed bright, for example by means of a metal brush. The molten (sintered) aluminum bodies emerging from the spray device namely react exothermically with the nickel to form intermetallic compounds of the nickel aluminide type, which are the Junction tail-applied metal a remarkable

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Mechanical resistance values that relate to the metallurgical diffusion of the aluminum in the foil is due.

Like "when applying the metal layer to the end of the The metal for fixing the end piece on the separating element can be carrier in any known manner of injection molding be applied without thereby departing from the scope of the present invention, for example by means of a chemical flame burner, an electric arc burner or a plasma torch.

The element for the separation of gaseous compounds, which has been prepared by the process of this invention _s corresponds perfectly with the requirements in respect to the effectiveness of separation, the mechanical resistance and chemical inertia, which are placed on such a product.

Patent claims:

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Claims (1)

Claims 1. A method for producing a permeable microporous ceramic element, characterized in that the ends of a porous tube, which is the carrier of the element, by spraying on in the heat metallized, a thin layer of a microporous powder is applied to the inner wall of the support, which this s serves to close the gaseous compounds from one another separate, the applied layer compacted (compressed) and fixed metallic end pieces at the ends of the element by spraying on the joints in the heat of a metal between the end pieces and your element. 2. The method according to claim 1, characterized in that a ductile metal is used as the metal which is sprayed onto the ends of the ceramic tube support ^T .vird, which has a good resistance to corrosion by fluorine-containing gases and which is preferably is aluminum or an aluminum alloy. 5. The method according to claim 1 and / or 2, characterized in that the sprayed onto the ends of the pipe support Metal coating is continuous and the end face (the cross section) and approximately equal lengths of the inner wall and the outer wall of the carrier. " 4-, method according to at least one of claims 1 to 3, characterized in that the length of the metal layer applied to the outer wall of the carrier is limited by Inserting one made of glass-shaped carbon. Mask between the spray device (spray gun) and the carrier in the jet of the melted (sintered) Particle. 709827/0898 ORIGINAL INSPECTED 5. The method according to at least one of claims 1 to 4, characterized in that it limits the length of the metal layer applied to the inner wall of the end of the carrier is by directing a stream of gas, in particular a stream of air, onto the opposite end of the carrier, which pushes the particles back towards the outside of the carrier. 6. The method according to at least one of claims 1 to 5t characterized in that the metal using a spray device with a chemical flame, with an electric arc or with a plasma. 7. The method according to at least one of claims 1 to 6, characterized in that the applied layer compressed (compressed), and then subjected to a heat treatment. 8. The method according to at least one of claims 1 to 7 » characterized in that cylindrical metal end pieces are connected to the ends of the element and they are attached thereto fixed by a metal coating that is sprayed onto the connection points between the end pieces and the element will. 9. The method according to at least one of claims 1 to 8, characterized in that the end pieces made of nickel or consist of a nickel alloy and that the surface which must receive the metallic coating, in a mechanical way is scrubbed bright with a metal brush. 10. The method according to at least one of claims 1 to 9 * characterized in that the metal which ensures the fixation of the end pieces on the element is is aluminum or an aluminum alloy. 709827/0898 -1- 11 · Method according to at least one of claims 1 his
10, characterized in that the length of the metallic coating, which ensures the fixation of the end pieces, on the ceramic element is approximately equal to that of the
Is a metal layer that has been applied to the outer wall and to the inner wall of the carrier. 709827/0 8 98